In low-pressure gas discharge lamps, a discharge is ignited and maintained in a gaseous discharge medium, in order to generate UV light or—by way of a phosphor—visible light. The gas fill contained in a discharge vessel of the lamp generally contains mercury (Hg), which originates from a Hg source that is present in the discharge vessel. The addition of Hg must be adapted in such a way that a Hg vapor pressure which is favorable for the light generation efficiency results in long-termed lamp operation.